The present invention relates to internal combustion engines of the type wherein the piston comprises the movable part of a pump or compressor for supplying air to the combustion space of a cylinder of the engine. Such engines may be fueled by carburetor means or fuel injection means.
Known two-cycle engines of this type have a number of drawbacks. A principal problem is the fact that high torque is obtainable only over a limited rpm range. As a result, when used in an automotive vehicle or the like, an inordinate amount of shifting of the associated transmission is required to maintain a high torque output under varying conditions of operation.
Known two-cycle engines exhibit an impulse scavenging which exhibits varying pressure during scavenging, whereas a constant pressure scavenging would be desirable. Furthermore, these known engines have a low scavenging ratio, whereas a high scavenging ratio is very desirable. Such engines employing carburetors suffer objectionable fuel-air mixture loss during the scavenging process of the operating cycle. Additionally, the fuel-air mixture provided to the cylinders of such engines may not be homogeneous. A simple carburetor does not satisfactorily meet the engine requirements during transient operation. The pressure within the cylinders of such engines is not constant at the beginning of the compression stroke as is desirable, but varies according to engine loading. Additionally, in these known engines, the expansion process is of fixed duration, whereas it would be desirable to vary or extend this expansion process.
The clearance volume of the compressor of known engines is excessive, and it is desirable to reduce such clearance volume to a minimum. Additionally, it would be highly advantageous to avoid or minimize direct contact between the compressed air and lubrication oil which may be within the crankcase.